Oh dear, dear me no.
If you insist that other people must weigh every impact on you and include you before making major personal decisions, you are creating an absolute mess of entangled entitlement for yourself and everyone else.
You and your sister are both entitled to your feelings, but having feelings does not give you veto power over someone else's life.
You are not owed a casting vote, a consultation, or any input on choices someone makes strictly for themselves, just as no one gets to dictate your job, your partner, or your friends. Personal decisions are not run by committee, no matter how close people may be.
Deciding another person’s wedding choice is yours to feel offended by confuses a choice made for themselves with a deliberate slight directed at you. You weren't being attacked by her choice not to tell any of you. You can want whatever you like, but that is not equivalent to another person's right to have auotonomy over their important decisions.
You cannot be deprived of an event you do not own. A wedding is a private choice, not an obligation owed to you or anyone else.
They did not do something TO or AGAINST you, they did something for themselves. It's not an active attack or insult to simply do what they want without kowtowing to what you or others might want. You're simply not part of the decision making, how you choose to feel about that is up to you.
I can see why the kept their choice private. They pre empted your (and other family members) main character syndrome rather effectively by doing so.